This is amazing! o.o I mean, just the card's design is wonderful. I like the Shiro/Satan one best... xD Shiro looks so awesome in your style! ♥ I want a set of Ao-X poker cards now. 8D But the whole composition of this artwork is amazing too. Mephisto is my fav anyways and he looks awesome. The whole dynamic in this artwork and the pinkish color. My I want to describe things more properly, but all I can say now is WOW F-A-N-T-A-S-T-I-C! ♥ I'm so gonna watch you now. *insert psycho soundeffect here* xD
I know chess is the game most commonly associated with Mephisto, but I keep thinking he would be world champion at card tricks. He seems to hold a good hand, there... Save for the Queen, I'd say that's... almost a Royal Flush? Was that an intended pun?
Shan't deny, I am fond of perspectives, and I love what you've done with the spiralling cards and with Mephisto. I have a little problem with his left arm, but it's nothing I would bother to go in and change if I were you.
Extra points for the colour scheme - so much bubblegum! x3